Method of concentrating nonmetallic minerals



April 30, 1940-v c. H, PEDbRlcK, JR., ET AL 2.198,972

METHOD 0F CNCENTRATING NONMTALLIC MINERALS Filed April l, v1938 INVENTORS TTORNEYS Patented Apr.' 3o, 1940 UNITE-o sTATEs METHOD CONCENTRATING NON- METALLIC MINERALS Charles H. Peddrick, Jr., Northvill'e, N. Y., and Joseph H. Weis, West Paris, Maine, assignors to Feldspathic Research Corporation,

New

York, N. Y., a corporation of Delaware Application April 1, 193s, serial No. 199,323

4 Claims.

This invention relates yto a method and means for concentrating minerals, particularly natural siliceous minerals such as feldspar, pyrophyllite, olivene, talc, kyanite, zircon, etc., and is a continuation in part of our application Serial No. 27,708, filed June 21, 1935.

'Ihe object of the invention is to provide an efllcient and commercially practical method and means for concentrating minerals by the separation of undesired mineral substances whose physical and chemical characteristics are -such that they cannot be removed byordinary methods of treatment, and its specific object is to separate and remove free silica or quartz from natural minerals of the above and other types.

In the preferred embodiment of the'invention the natural minerals are crushed, and preferably separated according to size, and are treated with an acid or gas containing a fluorine radical under temperature conditions suchthat the particles or granules are vrendered selectively susceptible to an electrostatic field. The mixture treated in this manner is then fed to an electrostatic separator wherein the free silica is removedwith a corresponding concentration of'the other ingredients.

The invention will be described as applied to the separation of free silica, usually inthe form of quartz, from natural minerals of the above mentioned type having physical and chemical characteristics such that the separation of the silica by physical or chemical methods is unsatisfactory.

As a specific example, the feldspar or other non-metallic mineral containingl free silica or quartz may be crushed or ground, as by means of crushing rolls, to reduce the same tolgranular particles of suitable size such as 10 to 200 mesh.

'I'he product is preferably graded into a plurality F. Below and above this temperature range inferior results are obtained, although an appreciable separation of free silica may be obtained at temperatures between 110 and 390" F.

The particles treated in the above manner are preferably dried and then fed to an electrostatic separator having a potential offrom 5,000 to 30,000 volts, wherein the treated -silica particles are caused to segregate toward one pole while the other particles segregate toward the other pole. The particles may be selectively separated into concentrates, middlings and tailings if desired,l each class falling or passing into separate receptacles or bins.

It is found that the potential on the electrostatic separator may be varied according to the material and according to the previous treatment, the above values being given by way of example only.

'I'his method may be used to'process graphic granite, pegmatites and other mineral mixtures the constituents of which are differently susceptible to an electrostatic fleld after treatment.

' In some instances it is found that one ingredient may be removed under certain conditions of time, temperature and voltage and another ingredient may be removed under other conditions. 25

While the exact reason for the selective action is not definitely known, we ascribe it to the formation of a coating of uorine or fluorides lon the particles which, under our temperature conditions, changes their electrostatic susceptibility. Whatever may be the exact explanation or the exact nature ofthe coating on the particles. the separation has been found to be successfully accomplished under the conditions above specied.

'Ihe various features and advantages of the invention will be described in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic illustration of an apparatus which may be used in carrying out the 4o invention; and

Fig. 2 is a chart which illustrates graphically the relation of temperature to quartz separation according to the method of our invention.

In Fig. 1 of the drawing, one form of apparatus 45 in which the above process can be carried out is shown as comprising a set of bins l which are adapted to receive different materials for treatment, for example non-metallic granules of different sizes. A set of gates 2 are adapted to con- 50 trol the discharge of material from said hoppers to chutes 3 which lead to a treating chamber or cylinder 4.

The treating cylinder 4 y may be rotatably mounted as by hollow shafts 5 and 6 which may 66 be journaled in bearings 1 and 8 respectively, carried by suitable supports 6 and I0. A driving means such as a belt pulley I I may be secured it is brought to the top for receiving the charge.

The reagent may be introduced into cylinder 4 from a receiver I6 connected to an inlet pipe I6 through a measuring device comprising a pipe I1 having a pair of spaced stop cocks I8 and I9. The capacity of the pipe II between stop cocks I6 and I9 determines the quantity of reagent which is added to the cylinder 4 as a single charge. The inlet pipe I6 may connect with a channel 20 in an inlet block 2| which may have a running fit with the hollow shaft 6 and may be sealed thereto by a packing gland 22. The inlet block 2| may be mounted on a stationary support 23. A blower 24 may be connected to the inlet pipe I 6 to force the reagent into the cylinder 4 and to mix a certain amount of air therewith.

Heated air or gases may be supplied to the cylinder 4 from a container 28 which may be heated by suitable means such as an electric heating unit 29. A blower 39 may have an intake pipe 3| connected to the container 28 and an outlet pipe '32 connected to a channel 33 in the inlet block 2I. A suitablethermostat 34 may beA employed to control the temperature within container 28.

The hollow shaft 6 may connect to an exhaust pipe 38. The cylinder 4 and the hollow shaft 5 have a lining 39 of a material adapted to withstand the reagent, for example a lining of rubber, lead or ceresin wax since a reagent having a fluorine radical is used. The receiver I5, inlet block 2I and other parts coming in contact with the reagent may be made of or lined with similar material.

The cylinder 4 is adapted to discharge the treated charge into a receiver 43 having a removable top 44 and terminating in a spout 45 which may be closed by a gate 46. The receiver 43 may be connected by a pipe 41 with the blower 39 and by a pipe 48 with the exhaust pipe 38, so that hot air or heated gases may be blown through said receiver.

The spout 45 is adapted to discharge the treated material to an electrostatic separator comprising a set of rolls 50 arranged with a series of bailles 5I so that the material falls in succession from one roll to the next and finally is discharged onto a conveyor 52 by which it is collected and conveyed to a convenient receiver (not shown). The rolls 50 constitute one pole of the electrostatic separator and may, for example, be connected to ground by a line 63. The opposite pole may comprise a set of rods 54 which may be connected to a source of high potential by a line 65. The rods 54 may be located above chutes 66 which discharge to a suitable discard receiver (not shown).

In the operation of this apparatus the feldspar or other non-metallic mineral is crushed and graded and the different grades are stored in the various bins I. The different grades are preferably treated separately as a more uniform product is thus obtained. A gate 2 is then operated to release the material from one bin into cylinder 4, after which the cover I2 is secured in place.

The reagent, for example hydroiluoric acid, iluosulphonic acid, or silicon tetraiiuoride gas, is

the stopcock I8 with the stop cock I9 closed so as to ll up the intervening pipe I1, then closing the stop cock I8 and opening the stop cock I9 to admit the measured quantity to pipe I6, whence it is blown by the blower 24 into cylinder 4. Warm. air at to V390 F., but preferably between and 280 F., is also blown into the cylinder 4 from container 28 by blower 39.

The cylinder 4 is rotated until the desired reaction has taken place. It is then stopped and the contents discharged into receiver 43. It may remain in this receiver a further period, if desired, under the influence of heat supplied from the blower 30 and is then passed to the electrostatic separator. Under the influence of the electrostatic field the treated particles of free silica are segregated toward the rods 64 and fall down chutes 56 into the discard. The concentrate, reduced in silica, falls onto conveyor 52 and is recovered for use.

The chart of Fig. 2 shows the relation of temperature to quartz separation according to the above method, this chart representing tests made on feldspar mined and processed at Spruce Pine. North Carolina. Two curves A and B are illustrated, comprising a band or range of results due to various irregularities in operation such as in the feed rate, acid rate, static irregularities, etc., which could not be controlled.

The curves A and B show that practically no separation of quartz from the feldspar takes place until the temperature of treatment with the iiuorine reagent islraised above 'l5-100 F. range representing the lower limits of the band. The optimum range of temperature for commercial operation, illustrated by Fig. 2, is between 170 and 280- F., and both above and below these temperatures the percent reduction in free quartz content with respect to temperature falls off rapidly. However, while inferior results are obtained outside the stated range of 170-280 F., it will nevertheless be noted that an appreciable separation of free quartz may be obtained at temperatures ranging all the way from 110 to 390 F.

#l original #2 original #3 original feldspar ieldspar feldspar Concentrate Concentrate Concentrate No. l No. 2 No. 3

Of course, the number and arrangement. of electrodes in the electrostatic separator may be changed as required. 'I'he chutes 56 may likewise withdrawn from the receiver I6 by first openingbe omitted if other means are provided to collect the tailings. The treatment may be repeated to further concentrate the mineral, or it may be repeated under different conditions to remove other ingredients. Also, since only one speciiic embodiment of the invention has been set forth for purposes of illustration, it will be evident that various other changes may be made in the details of construction and method of operation Without departing from the scope and spirit of the invention as dei-lned by the appended claims.

The invention claimed is:

1. Method of reducing the silica content of minerals which comprises reducing the minerals to fine particles, agitating said particles with a reagent of the class consisting of hydrouoric n acid, iiuosulphonic acid and silicon tetrailuoride gas while simultaneously subjecting same to a temperature of from to 390 F; for a period of time suicient to render the different mineral particles selectively susceptible to an electrostatic eld, subsequently drying the treated particles, and then subjecting the dried particles to an electrostatic field to cause particles of silica to segregate from the remaining constituents.

2. Method of reducing the free silica content of minerals which comprises reducing same to finely divided particles, treating the particles with k a reagent containing a fluorine radical while simultaneously subjecting same to a temperatureof from 110 to 390 F. for a period of time adapted to render the particles selectively susceptible to 3. Method of reducing the vfree silica content I of minerals which comprises reducing same to rfinely divided particles, treating said particles with a reagent containing a fluorine radical while simultaneously subjectingsame to a temperature of i to 280 F. for a period of time sufficient to materially'increase their selective susceptibility to an electrostatic eld, and then subjecting the treated particles' to an electrostatic eld to cause the free silica particles to selectively segregate from the remaining constituents.

4. Method of reducing the free silica content of minerals which comprises reducing same to finely divided particles, separating said particles into different batches according to size and separately treating each batch with a reagent containing a iiuorine radical while simultaneously subjecting same to a temperature of 170 to 280 F. for a period of time suiiicient to materially increase their selective susceptibility to an electrostatic field, drying the treated particles, and then subjecting the dried particles to an electrostatic eld to cause the free silica particles to selectively segregate from the remaining constituents.

CHARLES H. PEDDRICK, Jn. JOSEPH H. WEIS. 

